Rotary screw engine having adjustable internal feed and adjustable outlet control

ABSTRACT

An expansion engine of the rotary screw type having cooperative male and female rotors in which high pressure vapor enters the engine at the inlet end of the rotors through internal and centrally located inlet ports. A central and adjustable control piston functions to admit high pressure vapor to the interior of the rotors which then enters the cavities between the rotors for ultimate expansion. The control piston has an equalizing port for controlling the fluid pressure in the expansion chamber so it will not be less than the pressure in the exhaust chamber of the engine, thereby contributing to the efficiency of the engine.

nited States Patent Kocher 1s] 3,66,70 Apr. 18, 1972 [54] ROTARY SCREW ENGINE HAVING ADJUSTABLE INTERNAL FEED AND ADJUSTABLE OUTLET CONTROL [72] Inventor: Erich J; Kocher, Milwaukee, Wis.

[73] Assignee: Vilter Manufacturing Corporation, Milwaukee, Wis.

221 Filed: Sept. 9, 1970 [21] Appl.N0.: 70,759

[52] U.S. Cl ..418/185, 41,8/188,418/201,

, 417/295, 417/440, [51] Int. Cl. ..F01c 1/16, F03c 3/00, F04b 49/00 [58] Field of Search ..418/183, 185-188, 418/191, 201; 417/295, 440

[56] References Cited I UNITED STATES PATENTS 3,527,548 9/1970 Kocher et al. ..418/188 7 1,862,440 6/1932 Tacci ..418/188 2,519,913 8/1950 Lysholm ..417/440 3,545,895 12/ 1970 Weatherston et a1 ..418/188 Primary Examiner-Carlton R. Croyle Assistant Examiner-John .l. ,Vrablik Attorney-James E. Nilles [57-] ABSTRACT An expansion engine of the rotary screw type having cooperative male and female rotors in which high pressure vapor enters the engine at the inlet end ofthe rotors through internal and centrally located inlet ports. A central and adjustable control piston functions to admit high pressure vapor to the interior of the rotors which then enters the cavities between the rotors for ultimate expansion. The control piston has an equalizing port for controlling the fluid pressure in the expansion chamber so itwill not be less than the pressure in the exhaust chamber of the engine, thereby contributing to the efficiency of the engine.

5 Claims, 11 Drawing Figures PATENTEDAPR 18 I972 3, 656, 876

SHEET 1 [1F 5 BACKGROUND OF THE INVENTION The invention relates to rotary screw type engines having two complementary and intermeshing screws or rotors which are mounted within a casing so as to define an expansion chamber for the high pressure fluid that enters at the inlet end of the rotors. Various means have been provided in devices of this type for controlling the inlet of the vapor to the expansion chamber between the rotors. Various types of fluids can be used, such as steam or refrigerants and as Freon 113 made by duPont.

An example of such a prior art engine is shown in the U.S. Pat. No. 2,845,777, issued Aug. 5, 1958 to Nilsson et al. In that prior art device however, the inlet fluid was controlled by a valve located in the casing and which fed the vapor directly to the periphery of the rotor.

SUMMARY OF THE PRESENT INVENTION The present invention provides a rotary screw type engine having complementary rotors rotatably mounted within a housing to define an expansion chamber for high pressure vapor admitted at one end. More specifically, the invention provides an improved means and location for admitting the high pressure vapor to the rotors. This means consists of an axially adjustable control piston located in the rotors which functions to admit high pressure vapor through an adjustable port between the piston and the interior of the rotors so that the vapor is fed from an internal, central location in the rotors.

Another aspect of the present invention relates to such a control piston which also has a pressure equalizing port for controlling over expansion of the fluid in the rotors, which results in a pressure in the rotors which is less than exhaust pressure, thereby contributing to the over-all efficiency of the engine at reduced loads. This provides a variable release and reduces the losses due to cavity pressures in the engine below the engine exhaust pressure, thereby eliminating negative work.

The improved inlet control provided by the present invention permits the amount of fluid being introduced to the rotors to be varied depending on the load of the engine, so that the engine operates at maximum efficiency.

These and other objects and advantages of the present invention will appear hereinafter as this disclosure progresses, reference being had to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view through the male rotor of the engine and also showing its control piston;

FIG. 2 is a transverse sectional view taken along line 2-2 in FIG. 1;

FIG. 3 is a transverse sectional view taken along line 3-3 in FIG. 1, and showing the inlet ports and the equalizing ports in the control piston and male rotor;

FIG. 4 is a view similar to a portion of FIG. 1, but showing the control piston in the intake closed-position;

FIG. 5 is a diagrammatic view of the various parts which make up the vapor cycle in which the engine of the present invention is included;

FIG. 6 is a developed or flattened view of that portion of the control piston and showing the inlet and equalizing ports superimposed over the inlet ports in the rotor; 1

FIG. 7 is a transverse sectional view taken along line 77 in FIG. 1;

FIG. 8 is a perspective view of the control piston, a certain portion being shown as broken away;

FIG. 9 is a pressure volume diagram for an ideal Rankine cycle engine;

FIG. 10 is a pressure volume diagram for an engine with only the variable feed inlet but without the equalizing port in the control piston; and

FIG. 11 is a pressure volume diagram for an engine made in accordance with the present invention.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring first to FIG. 5, the complete vapor cycle is shown which includes the engine E provided by the present invention. A boiler B is provided in which heat is added to the working substance so as to keep it at a high pressure and converting it from the liquid to a vapor, thereby increasing its volume many times. The high pressure vapor from the boiler flows from the boiler to the engine via line 1 and is expanded in the engine to a low pressure, thereby producing a mechanical power, such as at the output shaft to drive a variable load 3. The low pressure exhaust from the engine via line 4 is conducted to a condenser 5 where it is reduced in volume and converted to a liquid. The liquid which leaves the condenser is then conducted via line 6 to a boiler fed pump 7 from which it is pumped back via line 8 into the boiler. Equalizing line 10 balances the pressures in the chambers at the opposite ends of the control pistons.

Thus, a closed system is provided in which a heating source I acts to heat the fluid.

Referring now to FIGS. 1, 3 and 7, the casing of the engine C is provided with a pair of parallel bores 11 and 12 in which are rotatably mounted, respectively, the male rotor MR and the complementary and interengaging female rotor FR. More specifically, the helical lobes 13 of the male rotor are engaged in the helical grooves 14 of the female rotor in the known manner and thus form an expansion chamber 15 with the casing, which chamber expands in volume from the inlet end of the rotors (the right end as viewed in FIG. 1) to the engine outlet or exhaust, that is, the left end of the rotors. The male and female rotors are fixed to and mounted for rotation with their respective shafts 16 and 17 (FIG. 7). These shafts are mounted in suitable anti-friction bearings 20 in the casing, and also suitable seals 21 are provided to prevent fluid leakage. The power output shaft 16 extends outwardly of the casing and is connected to the load.

It will be noted that the male rotor, adjacent its inlet end (FIGS. 1 and 3) has a series, for example four, of circumferentially spaced, inlet ports 25 and the female rotor has six inlet ports 26. These ports extend from the hollow interior 27 and 28, of the male and female rotors, respectively, and radially outwardly to the expansion chamber 15 defined by the rotors and the casing. Shaft 16 has a hollow end 16a which is press fit into the rotor.

As shown in FIGS. 1 and 7, the male and female rotors, adjacent their exhaust end also have a series of radially extending and circumferentially spaced ports 30 and 31, respectively. These ports act to conduct some of the vapor from the exhaust chamber 33 (FIG. 1), as-required, back through the equalizing port to prevent over expansion in the rotor. The low pressure vapor passes from the exhaust chamber through the outlet line 4.

A shiftable control valve member having a rotor feed port registerable with said inlet port of said rotor is provided as follows. Axially slideable control pistons 40 and 41 are provided, respectively in the bores 42 and 43 of the male and female rotors. These pistons have a generally hollow interior 44 into which high pressure is introduced from line 1, inlet passage 45 in the casing of the engine and then into the annular grooves 46 and 47 which are formed in the casing around the pistons 40 and 41, respectively (FIG. 2). The high pressure vapor then flows from the annular grooves 46 and 47 and through the circumferentially spaced ports 48 and 49 in the walls of the male and female pistons. Thus high pressure vapor is introduced in the interior of the pistons regardless of the axial position of the pistons.

The pistons 40 and 41 are of similar construction and function and act to feed their respective male and female rotors. Guide pins 52a between the pistons and casing prevent rotation of the pistons in their respective bores.

The pistons each have a feed port 50 for feeding fluid to the rotors, and an equalizing port 60 and as the construction of these ports in piston 40 is similar to piston 41, only one piston will be described.

Piston 40 has a rotor feed port 50 whose shape is shown in flattened form in FIG. 6. This equalizing port 60 in the rotor is of such shape that it progressively increases in area in relation to ports 25, as the piston is moved axially, to the right in the drawing. As the piston is moved by its control stem 52 in an axial direction to the left (as viewed in FIG. 1), from the open position shown in FIG. 1, the amount of vapor permitted to flow from the interior of the piston to the expansion chamber through the ports 25, decreases. Then when the piston has reached the closed position as shown in FIG. 4, the feed port 50 no longer registers with the ports 25 and therefore, no high pressure vapor is fed into the expansion chamber between the rotors.

By this means, the high pressure vapor can be metered, at full pressure, into the expansion chamber by means of the centrally located and adjustable ports at the interior of the rotors.

Means are also provided in each of the pistons to prevent over expansion in chamber 15. This means takes the form of the equalizing port 60 formed in the piston. The port is of a shape shown in flattened out form in FIG. 6 and it progresses in effective size as the piston is moved. The equalizing port 60, when the piston is in the position shown in FIG. 4, acts to equalize the pressure in the expansion chamber 15 with the exhaust chamber 33 through ports 25, central portion of the rotor and shaft 16, and ports 30.

In other words, the present invention relates to a closed system that does not exhaust to atmosphere, and the pressure is exhausted into chamber 33 at a certain value. When the piston has moved the feed port 50 to the closed position, the fluid within the expansion chamber of the rotors may become of a lesser value than the exhaust pressure in chamber 33. In such a situation, the rotors would tend to rotate in the reverse direction. To prevent this, the equalizing port 60 is provided so that the expansion chambers are open through the central portion of the rotor, to the exhaust chamber 33. In this manner, when the equalizing passage 60 is aligned with ports 25, the pressure in the expansion chamber is equalized with that in the exhaust chamber.

The axial position of the pistons can be controlled either manually or by automatic means attached to their stems 52. The stems are connected together so the pistons move together. For example, a cross clamp 62 (FIG. 4) is rigidly clamped to and between the stems 52 of pistons 40 and 41.

By having a control piston for each rotor, good charging of the expansion chamber results.

Various forms of fluid can be used which are liquid under certain circumstances and form a vapor under other circumstances. For example, steam or refrigerant may be used in the present invention, but refrigerants have proved to be more satisfactory because, among other things, a smaller condenser is required. Freon 113 made by the duPont Company has proved to be particularly desirable for use with the present invention.

In operation, the high pressure vapor enters the engine at the inlet of the rotors and forces the intermeshing rotors apart by wedging in between them. As the rotors turn, they cut off the inlet opening thereby trapping high pressure vapor in the small cavity formed. Since the helix of the male rotor lobe is opposite of the helix of the female rotor lobe, cavities are formed at the inlet of the rotors between the intermeshing lobes at their point of mesh. These cavities increase in size as the lobes recede from each other until the cavities reach the outlet end of the rotors. The vapor thus expands as the cavity lengthens and continues to exert turning effort to the rotors until the cavities reach the outlet end.

FIG. 9 shows the ideal Rankine cycle which is well known as the complete expansion engine of the ideal type and is used for generally all engines as a standard for comparison. The Rankine engine admits the working substance at constant pressure, then expands it isentropically to some lower pressure and finally exhausts all of the substance at this lower pressure. All three processes take place without any transfer of heat to or from the fluid as it passes through the engine. The available energy is represented by the area, a, b, c, d, under the curve.

In FIGS. 10- and 11, maximum energy is represented by the area bounded by a, b, c and d; these curves are determined by the amount of pressure admitted at the inlet of the engine.

FIG. 10 shows the cycle with variable feed inlet cut-off The area under the curves between the inlet pressure and outlet pressure represents useful work. The area under the exhaust pressure line c, d represents negative work which tends to turn the rotors backwards. This negative area must be subtracted from the useful work area above the exhaust pressure line in order to arrive at the net useful work at the driving shaft.

FIG. 11 shows the cycle of the engine provided by the present invention and in addition to the variable cut off shown in FIG. 10, also shows the results of the equalizing port. In this diagram, it will be noted that the variable release reduces the losses due to cavity pressures in the engine, that is the negative work, which is represented in FIG. 10 as the area between the discharge pressure line and the curves. It will thus be seen that by providing a quick equalization of pressure between the expansion chambers and the exhaust chambers, lost energy is held at a minimum.

Iclaim:

1. A rotary screw type engine having a casing and in which cooperative and interengaging male and female rotors rotate to define an expansion chamber, one of said rotors having an internal inlet port in and adjacent one end for conducting high pressure fluid to said chamber, a piston type control valve member located centrally within and in concentric alignment with one of said rotors and having a feed port registerable with said rotor inlet port, said valve member being slideable axially between a feeding position in which said valve member feed port is aligned with said rotor inlet port and a position closed in which said ports are not in registry, means for equalizing pressure on each end of said valve member, a high pressure vapor inlet passage means extending from outside said casing and to said valve member feed port for conducting high pressure vapor thereto for charging said expansion chamber with vapor when said valve member is moved to said feeding position, and an exhaust outlet in said casing and located at the other end of said rotors for discharging fluid from said expansion chamber.

2. A rotary screw type engine having a casing and in which cooperative and interengaging male and female rotors rotate to define an expansion chamber, one of said rotors having a central bore, an inlet port in and adjacent one end of said one rotor and located between said bore and said chamber, a control piston having an open interior and slideable in said bore and also having a feed port extending from its interior and through its periphery, said feed port registerable with said rotor inlet port, said piston being axially slideable in said rotor between l a feeding position in which said piston feed port is aligned with said rotor inlet port and (2) a closed position in which said ports are not in registry, means for equalizing pressure on each end of said piston, a discharge outlet in said casing and located at the other end of said rotors for discharging fluid from said expansion chamber, and a high pressure vapor inlet passage means extending into the interior of said piston for conducting high pressure vapor thereto for charging said expansion chamber with vapor via said piston feed port when said piston is moved to said feeding position.

3. An elastic fluid operated rotary engine having a casing, cooperative and interengaging male and female rotors rotatable in said casing to define therewith an expansion chamber, one of said rotors having a generally centrally located inlet port in and adjacent one end and extending into communication with said chamber, a shiftable control valve member having a feed port registerable with said rotor inlet port, said valve member being shiftable between a feeding position in which said valve member feed port is aligned with said rotor inlet port and a positionclosed in which said portsare not in registry, a high pressure vapor inlet passage means extending intothe interior of said piston for conducting high pressure vapor thereto for charging said expansion chamber with vapor via said valve member feed port when said valve member is moved to said feeding position, an equalizing port in said valve member and also registerable with said rotor inlet port, and an exhaust outlet in said casing and located at the other end of said rotors for discharging fluid from said expansion chamber, said valve member equalizing port being in communication with said exhaust outlet, when said valve member feed port is moved to the closed position, whereby the expansion chamber of said rotors can be vented via said valve member equalizing port directly to said exhaust outlet.

4. A rotary screw type engine having a casing and in which cooperative and interengaging male and female rotors rotate to define an expansion chamber, one of said rotors having a central bore, an inlet port in and adjacent one end of said one rotor and located between said bore and said chamber, a control piston having a hollow interior and slideable in said bore, said piston having a feed port extending through its periphery from its interior, said feed port registerable with said rotor inlet port, said piston being axially slideable in said rotor between a feeding position in which said piston feed port is aligned with said rotor inlet port and a position closed in which said ports are not in registry, an equalizing port in said piston and also registerable with said rotor inlet port, an exhaust outlet in said casing and located at the other end of said rotors for discharging fluid from said expansion chamber, said piston equalizing port being in communication with said exhaust outlet when said feed port is in a closed position, whereby the expansion chamber of said rotors can be vented via said piston equalizing port directly to said exhaust outlet, and a high pressure vapor inlet passage means extending into the interior of said piston for conducting high pressure vapor thereto for charging said expansion chamber with vapor via said piston feed port when said piston is moved to said feeding position.

5. A rotary screw type engine having a casing in which cooperative and interengaging male and female rotors rotate to define an expansion chamber, said rotors each having a central bore, an inlet port in and adjacent one end of each of said rotors and located between said bores and said chamber, a control piston having a hollow interior and slideable in each of said bores and also having a feed port registerable with its respective rotor inlet port, said pistons being axially slideable in their respective rotor between a feeding position in which their piston feed port is aligned with its respective rotor inlet port and a position closed in which said ports are not in registry, a high pressure vapor inlet passage means extending into the interior of said pistons for conducting high pressure vapor thereto for charging said expansion chamber with vapor via said piston feed ports when said pistons are moved to said feeding position, an equalizing port in each of said pistons and also registerable with its respective rotor inlet port, an exhaust outlet in said casing and located at the other end of said rotors for discharging fluid from said expansion chamber, said piston equalizing ports being incommunication with said exhaust outlet when said feed ports are in the closed position, whereby the expansion chamber of said rotors can be vented via said piston equalizing ports directly to said exhaust outlet, a control stem for each of said pistons, and means for causing said pistons to move in unison. 

1. A rotary screw type engine having a casing and in which cooperative and interengaging male and female rotors rotate to define an expansion chamber, one of said rotors having an internal inlet port in and adjacent one end for conducting high pressure fluid to said chamber, a piston type control valve member located centrally within and in concentric alignment with one of said rotors and having a feed port registerable with said rotor inlet port, said valve member being slideable axially between a feeding position in which said valve member feed port is aligned with said rotor inlet port and a position closed in which said ports are not in registry, means for equalizing pressure on each end of said valve member, a high pressure vapor inlet passage means extending from outside said casing and to said valve member feed port for conducting high pressure vapor thereto for charging said expansion chamber with vapor when said valve member is moved to said feeding position, and an exhaust outlet in said casing and located at the other end of said rotors for discharging fluid from said expansion chamber.
 2. A rotary screw type engine having a casing and in which cooperative anD interengaging male and female rotors rotate to define an expansion chamber, one of said rotors having a central bore, an inlet port in and adjacent one end of said one rotor and located between said bore and said chamber, a control piston having an open interior and slideable in said bore and also having a feed port extending from its interior and through its periphery, said feed port registerable with said rotor inlet port, said piston being axially slideable in said rotor between (1) a feeding position in which said piston feed port is aligned with said rotor inlet port and (2) a closed position in which said ports are not in registry, means for equalizing pressure on each end of said piston, a discharge outlet in said casing and located at the other end of said rotors for discharging fluid from said expansion chamber, and a high pressure vapor inlet passage means extending into the interior of said piston for conducting high pressure vapor thereto for charging said expansion chamber with vapor via said piston feed port when said piston is moved to said feeding position.
 3. An elastic fluid operated rotary engine having a casing, cooperative and interengaging male and female rotors rotatable in said casing to define therewith an expansion chamber, one of said rotors having a generally centrally located inlet port in and adjacent one end and extending into communication with said chamber, a shiftable control valve member having a feed port registerable with said rotor inlet port, said valve member being shiftable between a feeding position in which said valve member feed port is aligned with said rotor inlet port and a position closed in which said ports are not in registry, a high pressure vapor inlet passage means extending into the interior of said piston for conducting high pressure vapor thereto for charging said expansion chamber with vapor via said valve member feed port whcn said valve member is moved to said feeding position, an equalizing port in said valve member and also registerable with said rotor inlet port, and an exhaust outlet in said casing and located at the other end of said rotors for discharging fluid from said expansion chamber, said valve member equalizing port being in communication with said exhaust outlet, when said valve member feed port is moved to the closed position, whereby the expansion chamber of said rotors can be vented via said valve member equalizing port directly to said exhaust outlet.
 4. A rotary screw type engine having a casing and in which cooperative and interengaging male and female rotors rotate to define an expansion chamber, one of said rotors having a central bore, an inlet port in and adjacent one end of said one rotor and located between said bore and said chamber, a control piston having a hollow interior and slideable in said bore, said piston having a feed port extending through its periphery from its interior, said feed port registerable with said rotor inlet port, said piston being axially slideable in said rotor between a feeding position in which said piston feed port is aligned with said rotor inlet port and a position closed in which said ports are not in registry, an equalizing port in said piston and also registerable with said rotor inlet port, an exhaust outlet in said casing and located at the other end of said rotors for discharging fluid from said expansion chamber, said piston equalizing port being in communication with said exhaust outlet when said feed port is in a closed position, whereby the expansion chamber of said rotors can be vented via said piston equalizing port directly to said exhaust outlet, and a high pressure vapor inlet passage means extending into the interior of said piston for conducting high pressure vapor thereto for charging said expansion chamber with vapor via said piston feed port when said piston is moved to said feeding position.
 5. A rotary screw type engine having a casing in which cooperative and interengaging male and female rotors rotate to define an expansion chamber, said rotors each having a central bore, an inlet port in and adjacent one end of each of said rotors and located between said bores and said chamber, a control piston having a hollow interior and slideable in each of said bores and also having a feed port registerable with its respective rotor inlet port, said pistons being axially slideable in their respective rotor between a feeding position in which their piston feed port is aligned with its respective rotor inlet port and a position closed in which said ports are not in registry, a high pressure vapor inlet passage means extending into the interior of said pistons for conducting high pressure vapor thereto for charging said expansion chamber with vapor via said piston feed ports when said pistons are moved to said feeding position, an equalizing port in each of said pistons and also registerable with its respective rotor inlet port, an exhaust outlet in said casing and located at the other end of said rotors for discharging fluid from said expansion chamber, said piston equalizing ports being in communication with said exhaust outlet when said feed ports are in the closed position, whereby the expansion chamber of said rotors can be vented via said piston equalizing ports directly to said exhaust outlet, a control stem for each of said pistons, and means for causing said pistons to move in unison. 